UML Weekend Crash Course™ - To Parent Directory

Session 7—Building the Use Case Narrative 77
Did you find the error in the Use Case diagram In Table 7-5, the dialog said, “The system
asks for the location of the item and unfilled quantity (from the LocateProduct Use Case).”
You need to add an dependency from the FillOrder Use Case to the
LocateProduct Use Case.
Use Case termination in the case study narrative
In the termination row in Table 7-6, you list all the ways that this Use Case could end. Use
Cases are not good at showing concurrency and interrupts, so this is often the only place to
identify things such as a cancel event and timeouts. You’ll need to use the Activity diagram
or even the Sequence diagram a bit later to flesh out the concurrency and interrupt requirements.
The termination section also provides you with a list of actions to consider when
writing the post-conditions.
Tip
No one diagram can show everything. This is why it is so important to understand
the purpose and features of each diagram. The diagrams are like tools
in a toolbox. You have to know which one to use for each task.
Most business applications like FillOrder will let you cancel the session at specific points
in the process. It is also usually wise to handle the condition where a user gets interrupted
and leaves a session open. The timeout termination could watch for a specified period of
inactivity before closing the transaction. And of course the user can actually complete the
process of filling the order or simply indicate that he is done.
Table 7-6
The Fill Order Use Case Narrative: Termination
Field Name
Use Case termination
Field Description
The user may cancel
The Use Case may timeout
The user can indicate that he is done
The user can fill all items on the Order
Post-conditions in the case study narrative
Finally, in the Post-conditions row in Table 7-7, you list the conditions that must be true
when the Use Case ends. These conditions are especially important in that they reveal processing
steps that may need to be added to the dialog to ensure that the system is stable
when this Use Case is completed.